Thanks John,
However, your answer reflects what you can do on a Cisco router, but my
question is more regarding to what IP address scopes that are valid on the
Internet. When talking Class A, you can do whatever you want with 10.h.h.h
on your LAN, but the rest are public Internet addresses, and I am looking
for what's legal or not.
Looking at the RFC's, the network 128.0.h.h is reserved, and so is
191.255.h.h, which only gives you 128.1.h.h to 191.254.h.h public Internet
IP addresses within the valid Class B scope.
Ole
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Ole Drews Jensen
Systems Network Manager
CCNA, MCSE, MCP+I
RWR Enterprises, Inc.
[EMAIL PROTECTED]
http://www.oledrews.com/ccnp
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-----Original Message-----
From: John Biel [mailto:[EMAIL PROTECTED]]
Sent: Monday, December 18, 2000 11:45 AM
To: [EMAIL PROTECTED]
Subject: Re: IP addressses - Are networks 2^x or (2^x)-2 ???
IOS v11.3 to 12 requires the use of "ip subnet zero" command to allow 2^x
instead of (2^x)-2.
IOS v12 up enables this by default.
So with IOS 12 its:
Class A: 128 networks (minus loopback)
Class B: 16384 networks
Class C: 2,097,152 networks
with default 11.3 it is as you show below, however you can set "ip subnet
zero" to recover the use of them
with IOS previous to 11.3 it is as you state below.
(Taken from Exam Prep: Routing by Robert E. Larson et al p.31)
"Ole Drews Jensen" <[EMAIL PROTECTED]> wrote in message
2019FB428FD3D311893700508B71EBFB48499F@RWR_MAIL_SVR">news:2019FB428FD3D311893700508B71EBFB48499F@RWR_MAIL_SVR...
> Let me reconstruct my message.
>
> After having read through some more RFC's, I now believe that the
following
> is the truth. If you do not agree, please reply.
>
> CLASS A : 1.h.h.h - 126.h.h.h = 126 networks
> CLASS B : 128.1.h.h - 191.254.h.h = 16382 networks
> CLASS C : 192.0.1.h - 223.255.254.h = 2097150 networks
>
> and
>
> CLASS A : n.0.0.1 - n.255.255.254 = 16777214 hosts
> CLASS B : n.n.0.1 - n.n.255.254 = 65534 hosts
> CLASS C : n.n.n.1 - n.n.n.254 = 254 hosts
>
> Thanks,
>
> Ole
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Ole Drews Jensen
> Systems Network Manager
> CCNA, MCSE, MCP+I
> RWR Enterprises, Inc.
> [EMAIL PROTECTED]
> http://www.oledrews.com/ccnp
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> NEED A JOB ???
> http://www.oledrews.com/job
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>
>
> -----Original Message-----
> From: Ole Drews Jensen [mailto:[EMAIL PROTECTED]]
> Sent: Monday, December 18, 2000 8:21 AM
> To: '[EMAIL PROTECTED]'
> Subject: IP addressses - Are networks 2^x or (2^x)-2 ???
>
>
> I thought I knew it by heard now, but when I had to prove a point to
> someone, I grapped some of my books, and they all have different
> explanations. I therefore jumped to IETF's homepage and started surfing
> their RFC's. BUT...
>
> On RFC 943 (Assigned Numbers) it says on page 1:
>
> Class A has 7 bit network number which allows 128 (2^7) networks.
> Class B has 14 bit network number which allows 16384 (2^14) networks
> Class C has 21 bit network number which allows 2097152 (2^21) networks
>
> This looks right, because the MSB is 0 in a Class A, thus the 7 bits. It
is
> only 127 networks though, since 127.x.x.x is reserved. That is also
> explained later in the RFC. The MSB in Class B is 10, thus the 14 bits.
And
> finally, the MSB in Class C is 110, thus the 21 bits.
>
> On page page 10 however, it says that the maximum allowed networks are:
>
> Class A : (2^7 - 2) 126
> Class B : (2^14 - 2) 16382
> Class C : (2^21 - 2) 2097150
>
> It now looks like it follows the same rule as host calculations, where you
> cannot use all 0's or all 1's.
>
> I have looked through all my books (I have a lot) and they all have
slightly
> different opinions about this.
>
> What is the right answer?
>
> Class A is from 0.x.x.x to 126.x.x.x OR 1.x.x.x to 126.x.x.x ?
>
> Class B is from 128.0.x.x to 191.255.x.x OR 128.1.x.x to 191.254.x.x ?
>
> Class C is from 192.0.0.x to 223.255.255.x OR 192.0.1.x to 223.255.254.x ?
>
> Regarding SUBNET's, they all have the same explanation, but here it is
> anyway. If you use 192.168.1.0/28, you have 4 bits for the subnet and 4
bits
> for the hosts, which give you 2^4 - 2 = 14 subnets with 14 hosts each. I
am
> pretty sure that that is the right explanation.
>
> Thanks for any comments on this,
>
> Ole
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Ole Drews Jensen
> Systems Network Manager
> CCNA, MCSE, MCP+I
> RWR Enterprises, Inc.
> [EMAIL PROTECTED]
> http://www.oledrews.com/ccnp
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> NEED A JOB ???
> http://www.oledrews.com/job
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>
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